1. Technical Field
Aspects of the present invention relate to an inkjet recording device, and particularly to an ink pack and an ink cartridge for supplying ink.
2. Description of Related Art
An inkjet recording device configured to eject ink onto a recording medium in accordance with an input signal has been widely used. In general, such an inkjet recording device is provided with an ink cartridge to supply ink to an inkjet head. Inside of a case of the ink cartridge, an ink pack containing ink is accommodated. If an inkjet recording device runs out of ink, a user replaces the ink cartridge with new one.
FIG. 9 is a plan view of a conventional ink pack 100 illustrating a producing process of the ink pack 100. FIG. 10 is a plan view of the ink pack 100. As shown in FIG. 9, the ink pack 100 is formed by folding a flexible sheet member 102 (made of two layers of resin having property of a gas barrier) in two, welding (by a heat seal) peripheral parts of the folded sheet 102, and thereby forming a sheet welding part 103. A part of one of edges of the folded sheet member 102 is not welded so that a space (a tap attachment part 104) to which a tap 101 is inserted can be formed. The tap 101 is used to introduce ink contained in the ink pack 100 to the outside of the ink pack 100. The tap 101 has a rubber stopper (not shown) fitted thereto.
As shown in FIG. 10, by fitting the tap 101 into the tap attachment part 104 of the flexible sheet member 102 and welding an attached part of the tap 101 to the tap attachment part 104, a tap welding part 105 is formed. Consequently, a sealed space (a sealed ink chamber 106) which is to be filled with ink is formed in the flexible sheet member 102.
In Japanese Paten Provisional Publication No. 2000-238291 (hereafter, referred to as JP 2000-238291A), an ink pack for an inkjet recording device is disclosed. According to JP 2000-238291A, the ink pack can be formed as follows. A tube-shaped body is formed by welding longer edges of each second film (forming a side part of the ink pack) to longer edges of each first film (forming a flat part of the ink pack). Then, shorter edges of the flat parts are welded to each other so that the tube-shaped body is formed into a bag shape, and an ink supplying tap is welded to the other shorter side of the body. Next, a band-shaped joint part extending from a side of the body to an adjacent side is formed at each corner of the body so as to strengthen parts of the body at which the films overlap with each other and to prevent the body from being damaged by the external pressure. Consequently, the ink pack having ink supplying performance can be formed.
As described above, the flexible sheet member 102 is welded to the tap 101. There is a possibility that a resin dissolves from the flexible sheet member 102 and the tap 101 when they are welded to each other, and the dissolved resin solidifies at the outside of an appropriate welding range. Hereafter, such a dissolved resin is referred to as a poly pool. If such a phenomenon occurs in the ink pack 100, the poly pools 107 appear at the inside edge of a junction part of the flexible sheet 102 and the tap 101 (i.e., the inside of the sealed ink chamber 106), as shown in FIG. 10.
Hereafter, a relationship between the strength of the poly pool 107 and the strength of the ink pack 100 will be explained. FIG. 11 is an enlarged partial side sectional view of the ink pack 100. In general, the ink pack 100 is lightweight and flex. Therefore, if an external pressure acts on the ink pack 100 or if ink swings in the ink pack 100 during transport of the ink cartridge accommodating the ink pack 100, stress acts on the ink pack 100 and therefore the ink sheet member 102 deforms according to the stress.
If stress acts on the ink pack 100, the ink pack deforms around the welding part between the tap 101 and the flexible sheet member 102, as an axis, i.e., the tap bends in the back and forth direction relative to the flexible sheet member 102, around the axis. In this case, stress directly acts on the poly pools 107 because the poly pools 107 exist at the welding part of the tap 101 and the flexible sheet member 102.
The strength of the poly pools 107 are relatively low because the excessive heat has been applied thereto during the welding. Therefore, the flexible sheet member 102 is ripped at the part around the poly pools 107. In a low ambient temperature environment, the strength of a film (i.e., the flexible member 102) further decreases. Therefore, a possibility that the flexible sheet member 102 is ripped increases. That is, the conventional ink pack has a drawback that the poly pool causes a break of the ink pack or damage to the ink pack.
The structure of the ink pack disclosed in JP 2000-238291A does not provide a solution to such a draw back of the conventional ink pack.